The advantages of a design of electronic devices having foldable casings or so called “folding casings” is well known especially in the field of mobile and portable electronic devices, respectively. The advantages refer primarily to the usability of such electronic devices that are formed of two casing halves, which are pivoted by a hinge mechanism joining the two casing halves with each other. A folding casing may have at least two folding positions, i.e. a close position, in which the both casing halves are stacked on the top of each other, and an open position, in which the casing halves' surfaces facing towards each other in the closed state, are exposed to a user. The close position offers an advantageous shape for carrying the device by a user, whereas the open position allows for presenting a relative large area to the user for implementing operating/control components such a keyboards, keypad, joysticks, touchpads etc. and for display components. Moreover, these components, which are presented to a possible user in the open position of the electronic device, are protected against external influences in the close position. Conventionally, a main body representing a first casing half implements electronics and operating/control components, while a top body representing a second casing half implements display components. Such aforementioned electronic devices with folding casings are known and employed for laptop and notebook computers, mobile phones, digital personal assistants, mobile communicators etc. only to list a selection of examples.
The hinge mechanism which provides for the junction of the casing halves and which allows for pivoting about at least one pivot axis is subject to several functional constraints. One constraint is focused by the design of the hinge mechanism itself and a second main problem emerging with the enabling of traversing electrical conductors through the hinge mechanism to have electrical connectivity between electrical and electronic components, respectively, implemented in the casing halves.
A flexible material in form of a strip, flap etc. may allow realization of the hinge mechanism itself. Such a design of the hinge mechanism itself enables the pivoted operating of the hinge mechanism but this design is subjected to wear by the pivoting movements in parallel such that this design may only allow for a limited number of pivoting movements (up to a maximum of several hundreds). More stable against frequent use are hinge mechanisms, which are provided with articulated hinges with articulated axles.
The electrical conducting between two casing halves through the hinge mechanism is conventionally accomplished by flexible printed circuits (FPC), which are indeed printed wire boards (PWB), being manufactured from a flexible board material. Concerns refer to the electrical conductor and especially the mechanical stress applied thereto due to the bending and pivoting movements, respectively, as well as the protection of the electrical conductor against injury from external influences.
The bending radius of the electrical conductor determines the mechanical stress that can be applied to the electrical conductor by bending and pivoting movements. The bending radius is further determined by the dimensions of the hinge mechanism, which is primarily determined by the dimension constraints set by the size of the electronic device with folding casings. The smaller the dimensions of the electronic device, the smaller the dimensions of the hinge mechanism and therefore the smaller the bending radius such that consequently, mechanical stress, torsion, compressing, tension, etc. of the electrical conductor increases with decreasing the bending radius. The electrical conductor has to withstand the mechanical deformation effected by the bending movements applied thereon each time the hinge mechanism is operated and in particular the electrical conductor has to exhibit the ability to resist breakage thereof also after frequent bending cycles.
Furthermore, the electrical conductor has to be protected against accidental damage applied thereon from outside of the electronic device when the electronic device is in open position. A simple solution of this concern is to protect the electrical conductor by a covering such with a flap of flexible resistant protective material. But a simple coverage is normally not sufficient to protect against puncturing, cutting and any similar effects by sharp and pointed objects, respectively.
The U.S. Pat. No. 4,825,395 discloses a hollow articulated hinge mechanism, which allows for routing electrical conductors therethrough. The articulated hinge mechanism is designed to enable one half of the two-piece folding casing to be rotated by one full revolution about the other half of the two-piece folding casing. The electrical conductors are subjected to distributed torsional stress during rotation movements which is taught by the U.S. Pat. No. 4,825,395 to be superior to locally concentrated stress of compression and tension. The design of the disclosed hollow articulated hinge mechanism might be advantageous over conventional solutions enlightened above but has disadvantages, which contradict a common use. The space within the hollow articulated hinge mechanism for accommodating electrical conductors is limited due to the specific routing of the electrical conductors therethrough. Consequently, the number of electrical conductors is restricted. Moreover, the torsional deformation of the electrical conductors within the hollow articulated hinge mechanism also limits the number of electrical conductors to be routed through such that the concept of U.S. Pat. No. 4,825,395 is not universally applicable in the field of electronic devices with folding casings.